The present invention relates generally to heat conducting materials, and more particularly, to a thermal interface material that uses thermally conductive fiber disposed in a low- or non-outgassing polymer matrix material adapted for use in spacecraft applications.
There are several generally used classes of thermal interface materials. These include loaded organic materials, thermal gasket type materials, and thermal grease. Several thermal interface materials are discussed in the "Satellite Thermal Control handbook", for example, by David G. Gilmore, at pages 4-52 to 4-58.
Conventional loaded organic thermal interface materials use a highly loaded (organic) carrier with many conductive particles. With such conventional interface materials, the bond line thickness is minimized in order to maximize thermal performance. Unfortunately, in loaded silicone interface materials, for example, a thermal bottleneck exists because of the conductance through the matrix and at (many) particle-to-particle contact points. These conventional interface materials work relatively well when thin bond lines and flat surfaces are present.
To provide the desired thermal performance, the thermal gasket type interface materials must be subjected to high pressure, which impacts structural loads and can cause bowing of mounting panels, for example. Separation (zero pressure) may occur at some distance from bolts that secure the gasket. Consequently, use of such gaskets is generally limited to small scale applications, where bolt-to-bolt spacing is a relatively small distance.
The thermal grease interface materials provide relatively good thermal performance. However, the thermal grease interface materials have been found to be major sources of contamination, and are not generally used in spacecraft applications.
Prior art conducting materials also include Gelvet.TM., a material manufactured by Johnson Matthey, Inc. and AF Inter Connector material manufactured by Shin Etsu, for example. Both of these products use carbon fibers in a silicone matrix with the carbon fibers disposed normal to the interface surface. the AF material acts as an electrical conductor between two devices, while the Gelvet material is designed to conduct heat between heat sinks and heat generating devices. Both of these solutions are designed for electrical non-space applications and do not use a low- or non-outgassing polymer matrix material. It has also been found that the Gelvet material may also exhibit fiber damage during cutting of the graphitized carbon fiber and may have a less consistent distribution of fiber length.
Accordingly, it is an objective of the present invention to provide for an improved thermal interface material that uses carbon based fiber in a low- or non-outgassing polymer matrix for use in spacecraft applications.